For the first time, auditory research will be conducted on animals which are susceptible to atherosclerosis similar in pathology to that occurring in man. With a view towards potential illucidation of the pathophysiology of presbycusis as well as general modes of microcirculatory dysfunction in the body, White Carneau pigeons will be studied in age matched groups. First, sub-groups with normal diet and high cholesterol diet will be studied for potential blood-lipid rheology effects; next, sub-groups will be studied at intervals over 2 years as one group acquires diet induced atherosclerosi. Pigeons with diet induced lesions will be taken off high cholesterol feeding at one year and studied for another year on a normal diet to test for possible "regression" effects. Pigeons will have correlative studies of A.C. cochlear potentials, serum cholesterol, aorta plaque area, aorta plaque cholesterol content, heart vessel cross-section study, celloidin cross-section and whole mount light microscopy of the inner ears, and body organ histology. If presently available pilot data linking cochlear potential loss in the pigeons with the degree of atherosclerosis are upheld by this study, the microscopic studies will be primarily directed towards finding the type of inner ear lesion involved in the syndrome.